Gauss Weapons

This collection of gauss weapons use rare earth magnets to accelerate projectiles to damaging speeds. They work using the same concepts as a coil gun, but instead of just one projectile travelling along a length of guide track, there are many projectiles that work in a chain reaction. A series of magnets are placed at equal distances along the track. Each has a couple of large ball bearings on the muzzle side of the magnet. The first ball bearing is fired using mechanical force – like a spring mechanism – and accelerates as it approaches the magnet due to the attractive force of that magnetic field. When it impacts the magnet it sends one of the ball bearings on the opposite side down the track where it will accelerate when it nears the next magnet in the chain. The weapon above achieves a final projectile speed of about 68 miles per hour, breaking six fluorescent tubes in a row on at the right side of the apparatus.

Still prefer rail guns that use electromagnets? Check out this gauss pistol kit that is about as powerful as a BB gun.

That first video features Zoz Brooks, of Prototype This fame. I’ve been wondering what he’s been up to. I worked with him on an episode of the show, and his prototyping skills were monumental. I’d always suspected he’d be back on TV soon.

Let me get this straight. Basically when the ball hits the magnet, it destroys the magnetism in the magnet slightly so that the last ball can leave the magnetic field with a bit of a gain in kinectic energy? This would have to be the case since if the magnetic field were to remain at the same strength there would be not net gain in energy and the last ball would leave at a lower velocity then the first, due to friction. Am I right in saying that?

Where O=ball and x=magnet. The O closest to the x is attracted very strongly. The next O isn’t, and the last one is barely attracted. (Weak enough that if you tilt the apparatus it falls, but strong enough it stays there when horizontal.)

When the first O hits the x:

O –> xOOO

it sends its force through until the last O gets knocked off:

OxOO —> O

Its knocked off with greater force because as the first O gets closer to the x, it speeds up.

If this is laid out over and over (on a rail, hence the name: rail gun), then the overall speed increases.

On a side note, I used to do this with my MagnetiX sets all the time :D

A gauss gun like this works a bit like a lumpy hill where each successive ball rests against a hump that stops it from rolling down the hill on its own.

Each ball knocks the next over the hump, adding more than enough energy to set the ball rolling down the potential energy hill towards the next magnet and ball.

The total energy at the last ball is the potential energy each ball had in respect to the next magnet, minus the amount of energy required to free each ball from their resting magnet, plus the amount you added by pushing the first ball.

Not because they give off energy, but because you impart work into the magnet to change the spins of the electrons that give rise to the magnetic field.

Part of the energy of the ball hitting the magnet is lost to the magnet. The work done re-arranges the tiny magnetic domains into a more or less random configuration. You have to add work because turning the magnetic domains “against the grain” requires force. They try to turn back into the field.

But once you’ve managed to do so to most of them, the domains will make tiny loops and swirls and wiggles and the magnetic field will be contained completely inside the piece. The magnet is no more, and the energy you expended turns to heat as the magnetic domains snap into their new directions.

Changing this random configuration again requires work because now you have to break those loops and wiggles as they try to maintain themselves, and again the same thing happens. Once you get them all to snap in the same direction, the energy is released as vibration on the atomic level – heat.

So you’re never going to get energy out of a magnet. In fact, to do so you would actually need to extract the energy out of the spin field of the electrons themselves, because that’s the source of the magnetic field and its energy. It’s all there all the time, you’re just re-arranging it.

The sidelinked project is a coilgun. Railguns only very recently left hypothetical territory and operate under an entirely different principal. Grammar arguments on the other post are one thing, but a blog run by geeky people really shouldn’t be making a mistake like that.

I’ve played with coil and rail guns in the past, and studied enough of the theory to know that it’s sound. This, however, seems more more like some kind of perpetual motion voodoo… Although it MAY be possible to get usable energy out of this type of setup, as stated above, you’d be destroying your magnets in the process with diminishing returns after each shot. If you really want to use magnets, get some pencil-eraser sized NdFeB supermagnets and use them as coil-gun ammo – They blow iron slugs out of the water with the massively increased coupling effect.

…and HAD, do your math. 68mph is crap – That translates to 100 FPS. When I used to play paintball, our technologically craptacular guns were set from 265-300 FPS, depending on the fielld… That translates to getting shot with a marble ~200 mph – A little painful, but oh so much fun…

@lurker I agree. The energy used to accelerate the balls has to come from somewhere and the destruction of the magnetic field is the only place I can see it coming from. Otherwise it would be perpetual motion.

The energy comes from the accumulated potential energy of the configuration of the balls.

O = ballbearing
M = magnet

Initial configuration:

O…..MOO..MOO..MOO..MOO….

In this configuration, ball bearings 1, 3, 5, 7, and 9 (counting from the left) are held some distance away from their closest magnet.

Final configuration:

…..OMO..OMO..OMO..OMO….. >>>>O

At this point, ball bearings 1, 3, 5, and 7 are now closer to a magnet than they were before, and bearings 2, 4, 6 and 8 are no further away. MOst of the potential energy from the positions of ball bearings 1, 3, 5, and 7 have been transferred to ball bearing 9, with a small amount lost along the way to heating the apparatus.

This is high school physics, folks. Nobody should graduate without knowing how figure this out.